1. Field of the Invention
The invention relates to the field of methods and apparatus for peeling fresh fruit and in particular to a method and apparatus for peeling citrus fruits when the albedo is enzymatically degraded as part of the peel removal process.
2. Description of the Prior Art
The invention may be applied to articles other than citrus. However, since a principal application is to citrus fruit, reference will be made primarily to citrus fruit. A citrus fruit comprises an outer peel which adheres to the inner meat by means of an albedo layer. The meat, in turn, comprises a number of segments, each enclosed by a membrane. The segments are arranged about an axial core. The equator of the fruit is herein defined on the outer surface of its peel as the greatest circumference about its axis.
Although fruit, and in particular citrus fruit, is sold and consumed in large quantities with its peel intact, there is nevertheless a market demand where consumers or users of citrus fruit would prefer or even require that the fruit be provided whole and fresh, but peeled. Hand peeling of fresh citrus fruit is extremely time consuming, particularly if the albedo is to be removed from the fruit. The cost to hand peel large quantities of citrus fruit causes the delivery of peeled citrus products to be expensive and thereby diminishes or prohibits many of the market applications which might otherwise be available.
Therefore, the prior art has devised various apparatus and methods for peeling fruit, and in particular citrus fruit.
One class of such prior art methods involves mechanically peeling, cutting or skinning the peel from the fruit. Many types of mechanical peelers have been devised over the years. Such devices either require a fruit of relatively constant diameter; cutting the fruit, regardless of its size, down to a predetermined diameter, or employing a cutting mechanism riding on the surface of the fruit which assumes a predetermined thickness of the peel and its underlying albedo.
One of the more recent examples of such mechanized fruit cutting devices, which utilizes a sensed impedance between the cutter blade and a ground through the fruit, is shown by Webb et al, "Fruit Peeling Apparatus," U.S. Pat. No. 3,982,482 (1976); and Webb et. al., "Fruit Peeling Method," U.S. Pat. No. 4,065,582 (1977). Another device which mechanically cold peels citrus fruit is shown by Sage, "Apparatus For Cold Peeling Citrus Fruit," U.S. Pat. No. 4,318,339 (1982). Another approach, using a circular knife inserted between the meat and the peel, is shown by Schier, "Apparatus for Peeling Fruit, Such As a Lemon and Slicing the Rind," U.S. Pat. No. 3,853,050 (1974). The use of stripping rollers which repeatedly cut strips of peel from citrus is shown by Morikawa et al, "Prepared Citrus Fruit Processing Apparatus," U.S. Pat. No. 3,515,188 (1970).
A device which abrades or rubs the peel from the fruit is described by Warren, "Skin Separator," U.S. Pat. No. 2,776,690 (1957). Another example of the use of an abrading device to remove fruit peels is shown by Hart, "System For Peeling Fruits and Vegetables," U.S. Pat. No. 3,618,651 (1971). The individual measurement of each fruit and its mechanical manipulation to then individually orient it through a series of cutters is described by Hatch, "Citrus Fruit Peeling Machine," U.S. Pat. No. 4,729,299 (1988).
The prior art has also devised various methods whereby heating and cooling cycles are applied to the fruit or fruit product to remove its outer covering or skin. Such examples are shown by Harris et al, "Method For Thermally Blasting Outer Coverings From Food Products." U.S. Pat. No. 4,569,850 (1986); Weaver et al, "Peeling Fruits and Vegetables by Multiple Heatings and Coolings", U.S. Pat. No. 3,982,037 (1976); and Savage, "Process For Treating Citrus Fruits." U.S. Pat. No. 2,283,290 (1942).
Still further, the prior art has devised methods wherein the use of laser energy is applied to a fruit product to vaporize the skin, MacMurray et al, "Method of Removing Outer Protective Layer From Edible Materials Using Laser Energy," U.S. Pat. No. 4,839,131 (1989).
Chemical processes are available to loosen or remove the peel, usually involving the use of various types of alkali solutions. Such methods are illustrated by Mohri et al. "Method For Chemically Peeling Fruits and Vegetables," U.S. Pat. No. 4,220,670 (1980); Otsuka et al, "Composition For Chemically Peeling Fruits and Vegetables," U.S. Pat. No. 4,161,459 (1979); Otsuka et al, "Method For Chemically Peeling Fruits and Vegetables," U.S. Pat. No. 4,130,668 (1978); and Askienazy et al, "Method of Chemical Peeling of Fruits and Vegetables With an Alkanolamine," U.S. Pat. No. 3,970,762 (1976).
The art has also devised methods whereby the albedo and segment membranes of citrus fruits are degraded by the use of enzymes to produce individual segments, Bruemmer, "Method of Preparing Citrus Fruit Sections With Fresh Fruit Flavor and Appearance," U.S. Pat. No. 4,284,651 (1981). Another method is described in co-pending U.S. application Ser. No. 394,567 (1989), "Process For Enzyme Peeling of Fresh Citrus Fruit," Adams et al, assigned to the assignee of the present invention and incorporated by reference herein.
These methods, and in particular the latter one, are essentially natural processes which are merely accelerated versions of the breakdown of the albedo (pectin) layer of citrus peels caused by the pectinase naturally occurring therein. This natural phenomenon may readily be observed in untreated, overripe citrus fruits wherein the peel progressively loosens as the fruit ages.
However, the prior art describes no special means or apparatus for physically removing the peel which is loosened or degraded in some manner by the chemical process. Typically, chemical degradation of the citrus peel does not remove the peel from the fruit, but only tends to weaken its attachment. Thereafter, the peel must actually be removed from the fruit by conventional hand processes or using hand peeling tools.
What is needed is a method and apparatus for removal of the peel from citrus fruit or other fruits and vegetables, which can be automated and which is not subject to the complexities, inflexibility and unreliability of prior art mechanical cutting, stripping and peeling apparatus, and which can use to advantage peel degradation like that provided by chemical and enzymatic processes, but without the hazards or inefficiencies of fruit handling which may be connected therewith.